Task analysis

the slides present "task analysis" chapter in "Human Computer Interaction" book by ALAN DIX, JANET FINLAY,
GREGORY D. ABOWD, RUSSELL BEALE

1. TASK ANALYSIS HUMAN COMPUTER INTERACTION Reham Marzouk Institute of Graduate Studies & Research Human Computer Interaction Course Code: 1404811

2. AGENDA Introduction Task Analysis Approaches Task decomposition Hierarchical task analysis (HTA) Knowledge-based technique Task analysis for knowledge description (TAKD) knowledge representation grammar (KRG) Entity–relation-based analysis Source of information and Data collection Uses of Task Analysis

3. What’s Task analysis Task analysis is the process of analyzing the way people perform their jobs: the things they do, the things they act on and the things they need to know. One of the purposes of task analysis is to help in the production of training materials and documentation. For this purpose, analysis of existing systems is sufficient Task analysis is about existing systems and procedures; its main tools are those of observation in various forms

4.   What are the aims of Task Analysis Verifies that the set of actions employed by the user does accomplish the task Used to predict the time taken to learn a new task and become a proficient user of the particular application Used to predict the time taken for a proficient user to accomplish the set task To improve the delivery of information to the user

5. Scope of Task analysis Unlike goal-oriented models that understand the internal cognitive processes. Look more at the observable behavior of users than their internal mental state. Restricted to precisely this objective observable behavior. You should be interested in what, not why. Include some inferences about the user’s internal goals.

6. Task Analysis Approaches looks at the way a task is split into subtasks, and the order in which these are performed look at what users need to know about the objects and actions involved in a task, and how that knowledge is organized an object-based approach where the emphasis is on identifying the actors and objects, the relationships between them and the actions they perform. Entity–relation-based Analysis Knowledge-based Techniques Task Decomposition

7. Aims: describe the actions people do structure them within task subtask hierarchy describe order of subtasks Variant: Hierarchical task analysis (HTA) is typical of such an approach A hierarchy of tasks, subtasks and plans describing in what order and under what conditions subtasks are performed TASK DECOMPOSITION

8. Hierarchical task analysis (HTA)

9. Hierarchical task analysis (HTA) How does one produce such a hierarchy with attendant rules? What subtasks must be accomplished in order to perform the main task? Q Apply some form of stopping rule in order to decide when the tasks are basic enough A EX A rule, which is particularly appropriate when the aim is to design training materials, is the P × C rule. This says that if the probability of making a mistake in the task (P) multiplied by the cost of the mistake (C) is below a threshold, then stop expanding Another obvious stopping point is where the task contains complex motor responses (like mouse movement) or where it involves internal decision making

10. Warm a pot Errors & Omissions

11. Warm a pot Errors & Omissions

12. 3. make a pot

13. 3. make a pot Warm a pot

14. 3. make a pot

15. 3. make a pot Plan 5. 5.1 – 5.2 if desired 5.3

16. Make cups of tea

17. Fixed sequence

18. Fixed sequence Waiting for events

19. Fixed sequence Optional tasks Waiting for events

20. Fixed sequence Optional tasks Waiting for events Cycles

21. Fixed sequence Optional tasks Waiting for events Cycles Time sharing

22. Fixed sequence Optional tasks Waiting for events Cycles Time sharing Mixtures

23. Task Analysis Approaches looks at the way a task is split into subtasks, and the order in which these are performed look at what users need to know about the objects and actions involved in a task, and how that knowledge is organized an object-based approach where the emphasis is on identifying the actors and objects, the relationships between them and the actions they perform. Entity–relation-based Analysis Knowledge-based Techniques Task Decomposition

24. Knowledge-based technique Aim s : understand knowledge required to perform a task provide training material, how-to manuals; take advantage of common knowledge across tasks. Focus on: objects used in task actions performed Use taxonomies : represent levels of abstraction organization (grouping) depends on purpose listing all objects then remove unnecessary Declarative knowledge elicitation techniques : established convention, existing documentation asking users to list objects; card sorting structured interviews, listing nouns and verbs

25. Knowledge-based technique An example taxonomic structure every control has exactly one place in the hierarchy

26. Knowledge-based technique Depending on the expected use of the task analysis, we may require different structures An example taxonomic structure

27. Knowledge-based technique driver’s viewpoint the accelerator and the brake perform related functions, but they have no connection mechanically An example taxonomic structure

28. Knowledge-based technique An example taxonomic structure owner’s viewpoint hand brake has been put with the door locks as an aspect of parking, but it should also be used as part of ordinary driving

29. Knowledge-based technique An example taxonomic structure These decisions could be justified based on particular purposes, but others are purely arbitrary. We could just have easily classified the washers/wipers into front and rear first there are two attributes: ‘function’ (wash or wipe) and ‘position’ (front or rear)

30. Task analysis for knowledge description (TAKD) Task Analysis for Knowledge Description (TAKD) uses three types of branches in TDH taxonomies: XOR — object in exactly one branch AND — object must be in both OR — can be in one, many or none Uses a special form of taxonomy called Task Descriptive Hierarchy (TDH) A completed TDH can distinguish any two specific objects

31. Wash/wipe Example TDH - Task Description Hierarchy

32. Wash/wipe Example TDH - Task Description Hierarchy

33. OR branches arise where the object could fall into more than one of the categories

34. TAKD has a uniqueness rule, which demands that a completed TDH can distinguish any two specific objects.

35. Knowledge Representation Grammar (KRG) ‘/’ for AND branches, ‘()’ for XOR branches and ‘{}’ for OR branches For example kitchen item/shape(flat)/function{preparation, dining(for food)} Translating, this says: a kitchen item whose shape is flat AND its function is preparation OR dining for food. adopt simple hierarchies, rather than the more complex AND/OR/XOR TDH trees.

36. Generification produced object and action taxonomies can be used in order to produce generic descriptions of simple tasks we could describe each simple task as it is performed using similar term sentence in KRG KRG terms do not use the complete KRG description of each action and object, but instead opt for a generic description The choice of an appropriate level to ‘cut’ the tree is influenced by the number of different KRG sentences generic task sequences is looking at frequently occurring sequences of simple tasks and their representation in KRG sentences.

37. Example kitchen job(preparation) using a kitchen item/shape(dished)/function{preparation}/ kitchen job(preparation(beating)) using a kitchen item/shape(dished)/function{preparation}/ OR kitchen job(preparation) using a kitchen item/function{preparation} specific generic

38. Task Analysis Approaches looks at the way a task is split into subtasks, and the order in which these are performed look at what users need to know about the objects and actions involved in a task, and how that knowledge is organized an object-based approach where the emphasis is on identifying the actors and objects, the relationships between them and the actions they perform. Entity–relation-based Analysis Knowledge-based Techniques Task Decomposition

39. Entity–relation-based analysis Emphasis on objects, actions and their relationships Similar to object-oriented analysis, but includes non-computer entities emphasizes domain understanding not implementation Running example: `Vera's Veggies’, a market gardening firm Owner/manager: Vera Bradshaw Employees: Sam Gummage and Tony Peagreen various tools including a tractor `Fergie' two fields and a glasshouse new computer controlled irrigation system

40. Objects concrete objects actors composite objects human actors non-human actors Team: Vera, Sam, Tony Tuples: Fergie, plough things Vera, Sam irrigation computer spade, plough, glasshouse the customers

41. Agent Action Patient ‘the gardener dug the soil with the spade’ direct agent Indirect agent Vera may program the irrigation controller to come on at midnight Examples : Sam (agent) planted (action) the leeks (patient) Tony dug the field with the spade (instrument) Instrument who performs the actions which is changed by the action used to perform action

42. Example

43. Relationships between objects, actions and events

44. Relationships between objects, actions and events

45. SOURCES OF INFORMATION AND DATA COLLECTION Documentation the existing manuals, instruction booklets, training materials Observation Formal observation can occur in the field or in the laboratory Informal observation spend time watching people and chatting Interviews general set of questions, possibly asking the expert to describe a typical day, or task. lists of objects/actions associated with the task

46. SOURCES OF INFORMATION AND DATA COLLECTION Initial analysis The detailed analysis, of course, depends on the analysis method employed, but most start by trying to build up lists of elementary objects and actions. highlighting the nouns (which will be objects) and the verbs (which will be associated with actions). Sorting and classification production of hierarchies and sorting of entries by various attributes some are carried out by the analyst, but some requires subjective assessments by domain experts

47. USES OF TASK ANALYSIS Manuals and tuition Earliest techniques in task analysis were aimed at teaching novices how to perform a task. In particular, this was important for military training, for example how to disassemble and clean a rifle. Training had to be quick and efficient as conscripts in peacetime may only serve a few years before returning to civilian life, or in wartime may only survive a few months. The hierarchical structure of HTA can be used to structure manuals or course material. For example, we want to write a beginner’s manual on tea making based on the hierarchical task analysis

48. USES OF TASK ANALYSIS How to do it manual is often useful for initial training, but for structuring a course, or for more advanced training material, a more conceptual structure is better we can produce the shortened list of generic objects and actions by ‘cutting’ the taxonomic tree, and use these as the structuring principle For example : we may structure a cookery course as follows:

49. USES OF TASK ANALYSIS Task analysis can be used to help a user transfer from one system to another comparison of functionality is not sufficient as the crucial differences may be in procedures two systems may seem completely different in terms of detailed commands and presentation, but have similar high-level concepts or similar patterns of use. These common features should be brought out and can be used to help the user transfer knowledge from one system to another

50. USES OF TASK ANALYSIS 2. Requirements capture and systems design The task analysis of an existing system can help in two ways: the analyst can ask ‘Which of the existing objects, tasks, etc., should be in the new system?’ the formalized presentation of the existing state of affairs may help the client to clarify what the novel features are to be. TDH taxonomies can help the designer to choose an internal model for the system which matches the existing expectations of the users. This may, of course, be modified to accommodate novel features, but gives a reasonable first structure.

51. USES OF TASK ANALYSIS Task sequences obtained from a task decomposition can be used when designing the system’s dialog The order in which subtasks are performed in the system can be made to mirror that of the original job. If we know that a certain task is frequently performed, then we want it to be easy for the user to perform the subtasks in the appropriate order. Detailed interface design Taxonomies of tasks or objects may be used in the design of menus TDH trees are obviously most useful in this respect. An object/action may be found by several paths through the menus.